A disk drive is an information storage device. The most basic parts of a disk drive are an information storage disk that is rotated, an actuator that moves a slider carrying one or more transducers to various locations over the disk, and electrical circuitry that is used to write and read data to and from the disk. The one or more information storage disks are clamped to a rotating spindle. More specifically, storing data includes writing information representing the data to portions of tracks on a disk. The transducer includes two separate devices—a write transducer that writes information representing data to the disk and a read transducer or sensor that reads information from the disk.
Storing data includes writing information representing the data to the disk. Conventional disk drives with magnetic media organize data in concentric tracks. There is a constant goal in these storage devices to store increased amounts of data. Two ways of increasing the storage capacity of these storage devices include increasing the bit density, which means reducing the spacing between individual bits along the circumference of a concentric track or a substantially concentric track. The tracks can also be written as spirals in some applications. The bit density can be increased along the spiral path.
Another way to increase the capacity is to increase the track density. This involves writing the tracks more closely together. In some embodiments, a portion of a previously written track can be overwritten to produce tracks that are thinner or less wide. A portion of the original track is removed leaving a track thinner than the write width of a write element. The concept is referred as shingled writing. Shingled writing is generally a form of perpendicular magnetic recording that increases the areal density of magnetic recording. In shingle-written magnetic recording (SMR) media, a region (band) of adjacent tracks are written so as to overlap one or more previously written tracks. Unlike conventional tracks, which can be written in any order, the shingled tracks must be written in sequence. The tracks on an SMR disk surface are organized into a plurality of shingled regions (typically called I-regions) which can be written sequentially from an inner diameter (ID) to an outer diameter (OD) or from OD to ID.
As the density of the bits and tracks increase, magnetic information from one bit or collection of bits on a track may interfere or be combined with magnetic information from surrounding tracks. This includes interaction between a written track and prior and subsequent tracks. The interactions can be on adjacent tracks resulting in adjacent track interference (ATI), but are not limited to adjacent tracks. In some instances, the interaction can be several tracks away. These interactions are referred to as far track interference (FTI). FTI in some instances is the partial erasure of a track or tracks that are more than one track away from the track being currently written. Any inter-track interference results in diminished accuracy of read back data.